Mixing apparatus



March 12, 1940. F. CRADDOCK MIXING APPARATUS 2 Sheets-Sheet 1 Filed Oct. 24, 1938 A :it::

March 12, 1940, CRADDQCK 2,193,686

MIXING APPARATUS Filed Oct. 24. 1938 2 Sheets- Sheet 2 Frederic/f L. C'raddac/r Mamas/1PM Patented Mar. 12, 1940 UNITED STATES PATENT oFFicEf Claims.

apparatus play an important part in the final quality of the product. j Although various forms of mixing apparatus have been heretofore proposed, and several different types are in general use throughout the industries, they are not altogether successful. One reason why the present forms of apparatus fail to achieve the results desired is that little or no consideration has been given to the fundamental principles involved in the mixing of materials and the further fact that prior workers in this art have equipped tanks with mere marine type propellers, without regard to the action that should be exerted upon the material to be mixed or the particular problems or the principles involved in the mixing operation under consideration. As a matter of fact, in certain apparatus the action of the propellers has been so severe as to constitute a thrashing action and insome instances has effected separation rather than combination of the ingredients of the mixture undergoing treatment.

It is, accordingly, the primary object of this invention to provide a novel mixing apparatus embodying mixing elements which are so designed as to exert an extremely efiicient mixing action upon. the material, through a combined 40 mixing and disintegrating action, and without effecting a harmful thrashing action thereupon.

A. further important object is to devise novel mixing elements which embody portions designed to exert a strong propulsive action upon the material and cutting portions for effecting thorough disintegration of the material. It is another object to devise a novel mixerpropeller, which has large surfaces for propelling the material to be mxed and teeth portions in advance thereof for exerting a cutting and disintegrating action upon the material before it is subjected to a propelling action.

Further objects of the invention will become apparent as the specification proceeds in connection with the annexed drawings, and from the appended claims. In the drawings:

Figure 1 is a side elevational view of a mixing apparatus of my invention mounted on. a mixing tank; v

Figure 2 is a side elevational'view of two of the novel propellers or mixing elements of the invention, shown in place on the shaft;

Figure 3 is a side elevational view of one'of the propellers shown in Figure 2 and illustrates the parts as they appear when viewed in the direction of the line 3-3 of Figure 2;

Figure 4 is an enlarged sectional view taken substantially on the line 4-4 of Figure 2;

Figure 5 is a view similar to Figure 4 but illus trates a slightly modified form of the invention;

Figure 6 is an end View of a modified form of propeller of the invention;

Figure 7 is a side elevational view of the propeller shown in Figure 6; v

Figure 8 is a View similar to Figure 6, but illustrates a further modified form of propeller of the invention; and

Figure 9 is a side elevational view of the propeller shown in Figure 8.

With continued reference to the drawings, wherein like reference characters have been employed to designate like'parts throughout the several views thereof, referring first to Figure l, the apparatus comprises a combined motor and driving unit A which is mounted on a mixing tank 13 by means of a clamp assembly C, and it drives a pair of mixing assemblies designated generally as D. The propellers actupon the materials to be mixed and set up currents therein. as indicated by the arrows to successively and repeatedly present the material to the action of the propellers. 4 v

As seen more particularly in Figure 2, the driving mechanism comprises a main housing section it! and an auxiliary housing section or cover H, which is .detachably secured thereto. The housing sections are secured together by screws or any other suitable means (not shown) but as the combined motor and driving unit A is reserved for the subject matter of a separate application, it will not be further described. s

In the illustrated embodiment of the lYlVEIl-i tion, I have shown two propellers mounted on shaft 54, which is carried by a chuck 55 driven by driving unit A. The propellers both face in the same direction, but his to be understood that they may be mounted in any desired combination to produce the best results under the operating conditions at hand. The propellers are identical in construction and similar reference characters will be applied to both of them. Referring more particularly to Figures 2, 3 and 4, each propeller embodies a hub portion 64 and any suitable means may be employed to secure it to shaft 54. For instance, a set screw or the like is preferable in order that the propellers may be adjusted longitudinally on the shaft and thereby adapted to various mixing conditions.

I have found three-bladed propellers to be very effective in my apparatus, but it is to be understood that the invention is not limited to propellers embodying any particular number of blades as they may be increased or decreased in number as desired.

Three blades 65 extend substantially radially outwardly from hub 66 and they are provided with comparatively large propelling surfaces 66, which exert a strong propulsive action upon the materials to be mixed. Provided at the outer free edge of each propeller blade are a plurality of claws or finger-like projections which I have found to be extremely efficient in disintegrating and thoroughly mixing the materials because the claws exert a tearing, cutting or disintegrating action upon the material.

Each claw 6'! is provided with a sharp edge 68 and it is seen from Figure 3 that the claws extend out of the plane of the blade and project forwardly with respect to the direction of rotation of the blades, with the result that edges 68' are operative to cleave or cut any lumpy aggregations that may be present in the material. Also, even when the material does not contain lumpy aggregations, the fingers have been found to nevertheless exert a superior finely sub-dividing and intermixing action upon the materials, which makes complete intermixture possible in a much shorter time than with any of the apparatus heretofore proposed. As seen in Figure 2, each blade is provided with deep recesses 69 adjacent the claws 6i, and this has been found to be advantageous as eddy currents are set up between the fingers, which promote intimate inter-mixture of the components of the material undergoing treatment.

The novel propeller of the invention, therefore, possesses two separate but yet mutually cooperating functions. Claws 61 serve to disintegrate the material and also to interznix it, while surfaces [it serve to propel the material and circulate it so that it will be repeatedly and successively subjected to the action of the disintegrating claws.

Although I have illustrated in Figure l a double propeller assembly in which both proellers are disposed so as to propel the material in the same direction, it is to be understood that, if desired, they may be rightand lefthand, respectively, or oppositely disposed, so as to cause the material to be propelled in opposite directions. Also, if it is found desirable under the operating conditions at hand, one of the propellers may be replaced by a plain propeller, or, if desired, two of the propellers of the invention may be used in combination with a third plain propeller. It is to be also understood that, if desired, the blades of each individual propeller may vary in form. For instance, one propeller blade may be constructed as shown in Figures 2, 3 and 4, whereas alternate blades may be of plain configuration.

Some materials require a different type of disintegrating type of action, and in Figure 5 I have illustrated one form of propeller which has been found very effective in handling certain classes of material. In this form of the invention, blades 65 are provided with claws 61a, which are milled away at H to provide comparatively sharp knife edges 12.

In Figures 6 and 7 I have illustrated a still further modification of the invention adapted for handling certain classes of materials, and it comprises a hub 14 carrying a plurality of blades 15, having propelling surfaces of substantial area. The leading edge of each blade is provided with a plurality of teeth-like projections or fingers l7, and comparatively large spaces 18 are provided between adjacent teeth. Each tooth is provided with a pair of beveled faces 19 and 8! on the rear side thereof, thereby providing comparatively sharp side edges 32 and sharp leading edges 83, so as to exert a cutting or disintegrating action upon the material undergoing treatment.

In view of the fact that the teeth are located on the leading edge of the blades, they exert a cutting or disintegrating action upon the material and the material so disintegrated is then admitted upon and propelled by the surfaces 16 of the blades, which are comparatively large and set up a strong circulation in the tank.

In the event that it is desired to exert a more intense disintegrating action upon the material, a blade of the character shown in Figures 8 and 9 may be employed, and it will be observed that this blade incorporates the features of the blades of Figures 2, 3 and 4 and also the blade of Figures 6 and 7.

The propeller is provided with a hub on which a plurality of blades 86 are mounted. Since the claws 61b provided on the periphery of the blades are the same as those shown in Figures 2, 3 and 4, and the teeth Tia are the same as those shown in Figures 6 and 7, these parts will not be again described and. similar reference characters with the sub-script a, have been applied thereto.

If desired, the propellers of the invention may be used in various combinations. For instance, a propeller of the character shown in Figures 2, 3 and i may be mounted on a shaft with a propeller of the character shown in Figures 6 and 7 and/or Figures 8 and 9, and the appended claims are intended to embrace my invention when it assumes this form.

Although I have shown a motor and a gear mechanism for driving the propeller shaft at a reduced speed with respect to the motor, it is to be understood that if desired, the propeller shaft may be driven directly at motor speed or be associated with gearing to effect rotation thereof at a speed in excess of motor speed, depending upon the factors of the particular mixing job at hand.

In the drawings I have chosen to illustrate the For instance, it may be used in apparatus of the character where the propeller shaft extends through the wall of, and is permanently installed in, a mixing tank.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention. being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. An agitating device of the propeller type, said device comprising a plurality of propeller blades having propelling portions of substantial area, each of said blades terminating at its free end in a plurality of comparatively long, substantially parallelly disposed claws, for exerting a disintegrating action upon the material as it is mixed, each of said claws projecting from the free end of its blade in a forward direction with respect to the direction of rotation of the latter.

'2. The device defined in claim 1, wherein said claws have parallel side edges and terminate in sharp points for exerting a cleaving action upon the material as it is being mixed.

3. A mixing device adapted to be carried by a shaft and rotated at high speed in one direction,

, in a quantity of material to be mixed, comprisclaws for exerting a disintegrating action upon the material prior to contact of thelatter with the propelling portion of the blade, said claws each being generally triangular in transverse section and being disposed with, the baseof the triangle in the plane of said propelling portion of the blade by which it is carried, whereby each of said claws provides a pair of sharp edges adjacent the, propelling portion of said blades, for exerting a cleaving action upon the material.

4. The device defined in claim 3, wherein the leading edge of each blade between said claws is rounded and bevelled back on its rear face to provide a sharp edge lying substantially in the plane of said propelling portion and the sharp edges of said claws.

5. A mixing device adapted to be carried by a shaft and rotated at high speed in a quantity of material to be mixed, comprising a plurality of propeller blades mounted for rotation about said shaft as anaxis, each of said blades having a propelling portion of considerable area for exerting a strong propulsive action upon the material, and each of said propelling portions being provided at itsleading edge with a plurality of comparatively long finger-like members which lie substantially in the plane of said propelling portions and are operable to exert a disintegrating and tearing action upon the material before it is contacted by the propelling portion of said blade, said blades each being provided with a second set of finger-like members extending outwardly from their free ends for exerting a further disintegrating action upon the material, said second set of finger-like members also inclining forwardly from the free end, of each blade with respect to the normal direction of rotation thereof.

FREDERICK L. CRADDOCK. 

